1. Field of the Invention
The present invention relates to a method for transmitting sensing information in a wireless sensor network including a pair node; and, more particularly, to a method for transmitting sensing information in a wireless sensor network including a pair node by enabling each of a sensor node and a pair node, which are in the same target area and collect the same information, to transmit/receive the sensed information to/from each other.
This work was supported by the IT R&D program for MIC/IITA. [2005-S-101-02, “Development of UHF RF-ID and Ubiquitous Networking Technology”].
2. Description of Related Art
A pair node is a node that operates identically to a sensor node in the same target area. The pair node senses or collects the same information sensed or collected by the sensor node at the same time. The pair node and the sensor node transmit and receive the sensed information to/from each other. Therefore, the pair node can store both of information sensed by the pair node and the sensor node. Also, the sensor node can store both of information sensed by the sensor node and the pair node.
FIG. 1 is a diagram illustrating the transmission of sensing information in a wireless sensor network according to the related art.
As shown in FIG. 1, the wireless sensor network according to the related art includes sensor nodes 101, 102, 103, 104, and 105, parent nodes 106 and 107, and a sink node 108.
The sensor nodes 101 to 105 transmit the sensing information a1, a2, a3, a4, and a5 to the sink node 108 through the parent nodes 105 and 106. The parent nodes 106 and 107 may also have a function of sensing information.
The information stored in the sensor nodes 101 to 105 include node information including identification ID, PAN ID, and power source information, sensor information including a sensor type and a sensor ID, sensing information such as values that are obtained through sensing, and alarming information that is transmitted when a threshold value exceeds under predetermined conditions.
When a wireless sensor network is formed in a tree structure, the sensor nodes insert the above described information into a message having a predetermined format and transmit the message to an upper level node such as the parent nodes. The sensor nodes do not directly communicate with neighbor nodes having the same parent nodes. Thus, the sensor nodes have no information about neighbor nodes.
In case of using sensor nodes of a tree structured wireless sensor network in an indoor space, the indoor space does not have many obstacle factors for sensor nodes. However, sensor modules and communication modules of the sensor nodes may have many difficulties due to the physical and electric conditions of the outdoor space if the sensor nodes are used in an outdoor space.
FIG. 2 is a diagram illustrating the determination of difficulty in a wireless sensor network according to the related art.
As shown in FIG. 2, a sink node 208 receives sensing information b2′ and b5′ having error from sensor nodes 202 and 205 when sensor nodes 202 and 205 are having difficulties in a wireless sensor network according to the related art. That is, the sink node 208 determines that the sensor nodes 202 and 205 have difficulties based on the error in the received sensing information b2′ and b5′ from the sensor nodes 202 and 205.
The sink node could not receive the sensing information b2′ and b5′ having error if the sensor nodes 202 and 205 have difficulty to transmit the sensing information b2′ and b5′ to the parent nodes 206 and 207. In this case, the sink node could not determine that the sensor nodes have difficulties.
If a sensor node having the difficulty is separated far away from a user or is in a location where a user cannot reach easily, it is difficult to repair, manage, and replace the sensor node.
Since chips forming a sensor node have limited state information of the sensor node to provide, it is required to add additional routine or circuitry to detect the difficulty of the sensor node. Such additional routine and circuitry make the wireless sensor network having the sensor node complicated and also create additional cost. Therefore, it is not an effective way to determine the difficulty of the sensor node.